Processes for preparing highly pure lithium carbonate and other highly pure lithium containing compounds

ABSTRACT

The invention generally relates to methods of selectively removing lithium from various liquids, methods of producing high purity lithium carbonate, methods of producing high purity lithium hydroxide, and methods of regenerating resin.

RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 13/029,908,filed on Feb. 17, 2011, which claims priority to U.S. Prov. Pat. App.Ser. No. 61/305,213, filed on Feb. 17, 2010, which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to the field of selectively preparinghighly pure lithium carbonate and various other highly pure lithiumcontaining compounds.

2. Description of the Related Art

Lithium carbonate (Li₂CO₃) is typically produced commercially from twosources: (1) the extraction from pegmatite mineral sources such asspodumene, lithiophyllite, or lepidolite, which can be obtained throughtraditional mining; and (2) extraction from lithium-containing brines,such as those found in the Salar de Atacama in Chile, Silver PeakNevada, Salar de Uyuni in Bolivia, or the Salar de Hombre Muerte inArgentina. There are alternative brine sources, such as, geothermal,oilfield, Smackover, and relict hydrothermal brines. These brines,however, have not previously been commercially exploited.

There are a number of commercial applications for lithium carbonateincluding: use as an additive in aluminum smelting (molten saltelectrolysis); enamels and glasses; to control manic depression (whenused in its purer forms); and in the production of electronic gradecrystals of lithium niobate, tantalite and fluoride. High purity lithiumcarbonate is required for the fabrication of several materials inlithium ion batteries, such as, the cathode materials and electrolytesalts, and also in more avant-garde secondary batteries which requirehighly pure lithium metal.

In the case of lithium ion batteries, purified lithium carbonate may berequired for the fabrication of the cathode, as well as in the activematerials for cathodes such as, and without limitation, lithium cobaltoxide, lithium manganese oxide or lithium iron phosphate, as well as,mixed metal oxides, such as, lithium cobalt nickel manganese oxide.

Several processes currently exist for the removal of lithium fromlithium chloride-rich brines or other lithium containing liquids,however, none of the currently employed methods are suitable for theproduction of lithium carbonate containing low levels of magnesium andcalcium, thus limiting the ability of the lithium carbonate to be usedas a battery grade lithium product without first undergoing furtherpurification. Methods for extracting lithium carbonate from mineralsources, such as spodumene or lithium aluminum silicate ore (LiAlSi₂O₆),similarly produce materials that lack sufficient purity for use inbatteries. The purity of the resulting material using these processes isnot sufficiently pure for battery grade lithium metal production, or forpharmaceutical grade lithium carbonate. Therefore, there is a need for amethod for extracting lithium from lithium-containing brines and toproduce lithium salts such as chloride and carbonate of sufficientpurity to produce high-purity lithium metal.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to a method ofproducing high purity lithium carbonate. The method includes the stepsof reacting a first aqueous solution that includes a technical gradeLi₂CO₃ with CO₂ to form a second aqueous solution comprising dissolvedLiHCO₃. Unreacted CO₂ and insoluble compounds are separated from thesecond aqueous solution using a gas-liquid-solid separator to produce athird aqueous solution. Dissolved impurities are removed from the thirdaqueous solution by contacting the third aqueous solution with an ionselective medium to produce a fourth aqueous solution. In a fmal step,Li₂CO3 is precipitated from the fourth aqueous solution, wherein theprecipitated Li₂CO₃ has a purity of at least about 99.99%.

In certain embodiments, the technical grade lithium hydroxide has apurity of not greater than about 99%. In alternate embodiments, thetechnical grade lithium hydroxide has a purity of not greater than about99.9% purity. In certain embodiments, the insoluble compounds separatedfrom the second aqueous solution are recycled to the first aqueoussolution. In certain embodiments, the method includes the step ofpreheating the third aqueous solution to a temperature of about 50° C.before precipitating Li₂CO₃. In certain embodiments, the method includesthe step of supplying the third aqueous solution to a reverse osmosisapparatus to concentrate the Li₂CO₃, wherein the reverse osmosisapparatus is operable to remove CO₂ from the solution and cause Li₂CO₃to precipitate. In certain embodiments, the precipitated Li₂CO₃ has apurity of at least about 99.999%. In alternate embodiments, theprecipitated Li₂CO₃ has a purity of at least about 99.9999%.

In another aspect, the present invention is directed to a method ofproducing high purity lithium carbonate. The method includes the stepsof contacting an aqueous brine containing LiHCO₃ having a purity of lessthan about 99% with CO₂ at ambient temperature to form a second aqueoussolution comprising LiHCO₃ and dissolved ions. The method includes thestep of separating insoluble compounds from the second aqueous solutionusing a glass-liquid-solid reactor to form a third aqueous solution, thethird aqueous solution comprising LiHCO₃ and dissolved ions. The methodthen includes the step of extracting at least a portion of the dissolvedions from said third aqueous solution with an ion selective medium toform a fourth aqueous solution containing the dissolved LiHCO₃ andhaving a reduced concentration of dissolved ions relative to the thirdaqueous solution. The method includes the step of maintaining a constantpressure while carrying out the separating and extracting steps.Finally, the method includes the step of heating the fourth aqueoussolution to form solid LiHCO₃, gaseous CO₂ and dissolved impurities.

In certain embodiments, the insoluble compounds separated from thesecond aqueous solution are recycled to the first aqueous solution. Incertain embodiments, the method includes the step of supplying thesecond aqueous solution to a reverse osmosis apparatus, wherein thereverse osmosis apparatus is configured to operate at high pressures,thereby concentrating the Li₂CO₃.

In another aspect, a method for producing high highly pure LiPF₆. Themethod includes the steps of reacting high purity Li₂CO₃ with HF toproduce lithium fluoride solution, and then reacting the resultingsolution with PF₅ to produce LiPF₆. In certain embodiments, the highpurity lithium carbonate is produced according to methods describedherein. In certain embodiments, the HF is dispersed in deionized water.

In another aspect, a method of producing highly pure LiF is provided.The method includes the step of reacting high purity lithium carbonatewith HF gas in a fluidized bed reactor, wherein the LiF is highly pureand dry. In certain embodiments, the high purity lithium carbonate isproduced according to methods described herein.

In another aspect, a method of producing highly pure LiMnO₂ is provided.The method includes the step of reacting high purity lithium carbonatewith electrolytic MnO₂ to produce high purity LiMnO₂. In certainembodiments, the high purity lithium carbonate is produced according tomethods described herein.

In another aspect, a method of producing highly pure lithium cobaltoxide is provided. The method includes the step of reacting high puritylithium carbonate with cobalt oxide to produce high purity lithiumcobalt oxide. In certain embodiments, the high purity lithium carbonateis produced according to methods described herein.

In another aspect, a method of producing highly pure lithium ironphosphate is provided. The method includes the step of reacting highpurity lithium carbonate with high purity ferric phosphate to producehighly pure lithium iron phosphate. In certain embodiments, the highpurity lithium carbonate is produced according to methods describedherein.

In another aspect, a method of producing highly pure LiH₂PO₄ isprovided. The method includes the step of reacting high purity lithiumcarbonate with phosphoric acid to produce highly pure LiH₂PO₄. Incertain embodiments, the high purity lithium carbonate is producedaccording to methods described herein. In certain embodiments, themethod further includes reacting the LiH₂PO₄ with iron oxide to producelithium iron phosphate.

In another aspect, a method of producing highly pure lithium chloride isprovided. The method includes the steps of reacting a solution thatincludes deionized water and high purity lithium carbonate with gaseoushydrochloric acid to produce highly pure lithium chloride. In certainembodiments, the high purity lithium carbonate is produced according tomethods described herein.

In another aspect, a method of producing highly pure lithium hydoxide isprovided. The method includes the step of electrolyzing a solutioncomprising highly pure lithium bicarbonate. In certain embodiments, thehigh purity lithium carbonate is produced according to methods describedherein.

In another aspect, a method for producing highly pure lithium carbonateis provided. The method includes the steps of feeding a first aqueoussolution that includes a purified lithium chloride stream to anelectrolyzer equipped with a membrane or a separator, wherein the firstaqueous solution has a lithium chloride concentration of up to about 40%by weight to form a second aqueous solution comprising at least 10% byweight lithium chloride. The method includes the step of applying acurrent to the electrolyzer to produce a third aqueous solution in thecathode compartment that comprises greater than 4 wt % lithiumhydroxide. Optionally, the method includes cooling the third aqueoussolution and supplying the third aqueous solution and carbon dioxide toa carbonation reactor to produce a fourth aqueous solution comprisinglithium bicarbonate. The fourth aqueous solution is separated from thecarbon dioxide and lithium carbonate solids formed using agas-liquid-solid reactor, and filtered to remove trace impurities.Finally, the method includes the step of feeding the filtered fourthaqueous solution to a precipitation reactor maintained at a temperatureof at least about 95° C. to precipitate highly pure lithium carbonate.

In certain embodiments, the method includes the step of supplying thefourth aqueous solution following the filtration step to an ion exchangecolumn to remove divalent ions.

In another aspect, a method of regenerating an ion exchange resin usedin the production of lithium is provided. The method includes the stepsof: displacing a first aqueous solution comprising lithium from theresin with water, wherein the water is supplied at a low flow rate;removing displaced solids from the resin using a counter-current flow ofwater; removing divalent ions by contacting the resin with dilute acid;washing the resin to displace and dilute the acid on the resin;reactivating the resin by contacting with dilute sodium hydroxide; andwashing the resin with water.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristic novel features of the invention are set forth in theappended claims. So that the manner in which the features, advantagesand objects of the invention, as well as others that will becomeapparent, may be understood in more detail, more particular descriptionof the invention briefly summarized above may be had by reference to theembodiment thereof which is illustrated in the appended drawings, whichform a part of this specification. Note, however, that the drawingsillustrate only an embodiment of the invention and are therefore not tobe considered limiting of the invention's scope as it may apply to otherequally effective embodiments.

FIG. 1 is a schematic illustration of one embodiment of the presentinvention.

FIG. 2 is a schematic illustration of one embodiment of the presentinvention.

FIG. 3 is a cross-section of an exemplary reactor for the production oflithium bicarbonate.

FIG. 4 is a schematic illustration a method for resin regeneration.

FIG. 5 is a schematic illustration of a method of regenerating thecartridge.

FIG. 6 is a graph showing the variation in lithium hydroxideconcentration during four experimental runs.

FIG. 7 is graph showing cell voltage during operation of electrolysiscell to convert LiCl to LiOH.

FIG. 8 is a graph showing the reduction in current efficiency observedat different LiOH outlet concentrations.

FIG. 9 is a graph showing energy consumption for production of LiOH atvarious outlet concentrations of LiOH.

FIG. 10 is a graph illustrating the pH of the LiOH solution more or lessremains constant until the entire lithium hydroxide gets converted intolithium carbonate. The sudden drop in pH is associated with theformation of lithium bicarbonate and completion of carbonation reaction.

DETAILED DESCRIPTION

Definitions

As used herein the following terms shall have the following meanings:

The term “high purity lithium” or “highly pure lithium” means lithium inexcess of 99.9% purity.

The term “ultra high purity lithium” means lithium in excess of 99.999%purity.

As used herein, the term “a total lithium carbonate concentration”includes both dissolved lithium carbonate (Li₂CO₃) and lithiumbicarbonate (LiHCO₃).

As used herein, the term “weak liquor” means the filtrate solution fromthe lithium carbonate recovery, which has a total lithium carbonateconcentration between about 0.5 wt % and about 0.15 wt %, depending onoperating mode (heating, cooling, and flow rate), operating conditions,and system design parameters.

As used herein, the term “strong liquor” means the solution fromcarbonation reactor having a typical total lithium carbonateconcentration normally lying between about 4.0 and 5.0% by weight,typically about 4.4% by weight %, depending on operating mode (forexample, heating, cooling, flow rate), operating conditions, and systemdesign parameters.

Preparing High Purity Lithium Carbonate

Broadly described herein are methods of producing high purity lithiumcarbonate (Li₂CO₃). In a first embodiment, the process includes reactingan aqueous solution that include technical grade Li₂CO₃ (such as theLi₂CO₃ that can be purchased from a chemical supplier, for example,Chemetal, FMC, SQM, or other such suppliers) with carbon dioxide (CO₂)at temperatures above the freezing point of the solution, typicallybetween about −5° C. and 45° C., more particularly around about roomtemperature, to produce an aqueous solution that includes lithiumbicarbonate (LiHCO₃) and lithium carbonate (Li₂CO₃) dissolved therein.The step of contacting the lithium carbonate with carbon dioxide ispreferably at as low a temperature as possible. In certain embodiments,the lowest temperature possible without using external energy to achievean altered temperature is employed, for example at room temperature.Alternatively, a leachable ore solution that includes lithium may betreated with carbon dioxide at a temperature of between about −5° C. and45° C., to similarly generate a solution that includes both lithiumbicarbonate and lithium carbonate. Such lithium bicarbonate/lithiumcarbonate solutions may be used in the methods as described herein. Thissolution is often referred to as the strong solution, and can, forexample, have a concentration of lithium compounds up to about 45 g/L,typically having a concentration of at least about 35 g/L at atemperature of about 45° C. The reaction can be conducted in a singlereactor, but is preferably conducted in two agitated reactors arrangedin sequence, or in series of reactors, optionally including a coolingsystem to maintain the reaction temperature at a temperature that isabove the freezing point of the solution, preferably about 20° C. Themixture from the last of the reactors can be fed to a separation tank,where undissolved lithium carbonate, solid impurities, lithiumbicarbonate containing solution, and carbon dioxide can be separatedfrom each other. Stirred tank reactors may be used to prepare themixture, but other gas-liquid-solid contacting reactors may also beused. The solid can be recycled preferably to the first or, optionallyto a second carbonation reactor, if present, where the gases can berecovered and recycled back to the carbonation reactor. In embodimentswherein more than one carbonation reactor is employed, recovered carbondioxide can be recycled to one or more carbonation reactors. The liquidstream can then be fed to a filtration system which can be configured toremove any insoluble impurities that may be present, such as, silica,iron, magnesium, calcium and like compounds. In certain embodiments, thefiltration can utilize of a series of filters designed to progressivelyremove finer particles, such as for example, filters designed to removeparticles having diameters of 10 μm, 1 μm, 0.2 μm, 0.3 μm, or in analternate embodiment, a microfiltration system can be employed that issuitable to prevent colloidal iron (III) from contacting the ionexchange media in the subsequent step. Such a microfiltration system canbe tangential (also known as flow by microfiltration) or perpendicular(also known as flow through microfiltration).

The filtration step is followed by the use of a divalent selective ionexchange resin, to adsorb soluble divalent or trivalent ions, such asmagnesium, calcium, iron and the like, by selective ion exchange orother similar methods. Following the removal of the soluble divalent ortrivalent ions by selective ion exchange, the temperature of thesolution can then be raised or otherwise extracting or partiallyextracting the CO₂ to precipitate pure Li₂CO₃ in a second zone andpreferably returning at least a part of the solution to the carbonationreaction zone (items 40, 45 and 50 in FIG. 1) for economic reasons. Thiscan be done by, for example, by creating a vacuum and bubbling an inertgas, such as, nitrogen, air, argon, or the like, through the solution.Carbon dioxide can be recovered and recycled to the carbonation step.Undesirable monovalent cation impurities present remain in solution andapproximately 85% of the solution can be recycled back to the lithiumcarbonate dispersion step at the beginning of the process and theunrecycled solution is recovered for use in the regeneration of the ionexchange media. During the filtration step of the process, lithiumcarbonate can be recovered by suitable methods, such as, rotaryfiltration, band filtration or the like. Recovered solid lithiumcarbonate can then be subjected to washing, such as, counter currentwashing, and can include separate filtration zones for the recovery ofthe filtrate (weak liquor) and the washing solutions. Approximately 15%of the washing solution can be removed and combined with the recycledlithium carbonate solution and supplied back to the initial dispersionstep of lithium carbonate.

The ion exchange resin captures primarily divalent ions, such as,calcium and magnesium; however, other divalent ions that are present canalso be captured by the ion exchange resin. The final step of filtrationincludes an iron (III) selective filtration system, which can preventthe iron (III) coming in contact with the ion exchange media. This issignificant because if iron (III) is not removed prior to contacting theion exchange resin and is captured by the ion exchange resin it isdifficult to displace them from the ion exchange resins by standardmethods of regeneration of ion exchange resins. Once the ion exchangeresin capacity becomes exhausted, the solution can be switched to asecond ion exchange column to continue filtration of the solution andcapture of divalent ions.

Purity of Lithium Carbonate

In certain embodiments, the purity of the lithium carbonate can becontrolled by ratio of the recycle to bleed of the weak liquor (i.e.,the amount of the filtrate from the separation of lithium carbonate thatis withdrawn). In certain embodiments, the weak liquor may have alithium carbonate concentration of about 15 g/L. As the bleed ratio isvaried between about 100% and 0%, the quantity of soluble monovalentcations and some anions build up in the recycle solution. Thus, atgreater bleed rates, a higher the purity of lithium carbonate productcan be obtained. For example, it has been found that at a bleed ratio ofabout 15%, 99.999% pure lithium carbonate can be obtained. Similarly, ableed ratio of less than about 5% typically results in the production oflithium carbonate of about 99.9% purity, which is sufficient forelectrochemical/battery grade production lithium carbonate. Furthermore,the degree of washing greatly influences the purity of the lithiumcarbonate product and its final purity. Different wash ratios to productthrough put can be used to produce different grades of product purity.

The operation of the ion exchange system is heavily influenced by thevelocity of the strong solution through the ion exchange and by varyingthe velocity of the strong solution, lithium carbonate of varying puritycan be obtained.

In certain embodiments, the lithium carbonate granulometry andmorphology can be managed by increasing the degree of agitation and theresidence time in the precipitation vessel. As used herein, granulometrygenerally refers to the particle size and morphology generally refers tothe shape of the lithium carbonate compounds. In general, enoughagitation is necessary to ensure that insoluble particles are suspendedin solution, however excessive agitation can, in certain embodiments,result in a decrease in the average particle size. Increased agitationcan be achieved by increasing the recirculation rates. Alternatively, itcan also be increased by the addition of a mechanical agitator to theprecipitation vessel. In certain embodiments, the residence time can beincreased or decreased by either the volume of liquid contained in thevessel or by altering the flow rate. In certain embodiments, the vesselcan have a fixed size; however the amount or rate of addition of liquidto the tank can be used to control the residence time of the liquids,thereby indirectly controlling the granulometry of the lithium carbonateparticles, and to a lesser extent, the morphology of the lithiumcarbonate particles. Moreover, in certain embodiments, the morphology ofthe lithium carbonate can be modified by the addition of various metalions to the mixture which provoke an altered crystal growth. In certainembodiments, the lithium carbonate particles can have an averagediameter of less than about 100 μm, alternatively less than about 50 μm,alternatively less than about 10 μm.

The process described above does not remove phosphate or borate from thelithium carbonate product as both phosphates and borates typicallyprecipitate with lithium carbonate. It is therefore envisaged that, incertain embodiments, phosphates and borates can be removed from thestrong lithium bicarbonate liquor by passing the liquor through aphosphate adsorbing media such as alumina, or by utilizing a suitableion exchange media such as AMBERLITE™ IRA743 or alternatively by solventextraction.

The initial sulfate content in technical grade lithium carbonateobtained from brines is typically about 100 ppm. In certain embodiments,the sulfate concentration in high purity lithium carbonate can bereduced in a single pass to only 10 ppm, assuming a recycle ratio ofweak liquor of about 85%. The sulfate concentration of the lithiumcarbonate can be further reduced by additional recycling of the lithiumcarbonate through the whole process. For example, in certainembodiments, a product lithium carbonate stream that has been twicecycled through the process described above twice can have a sulfateconcentration of less than about 1 ppm.

In certain embodiments, an alternative approach reducing the sulfateconcentration is to increase the bleed ratio to between about 50 and100%, rather than the more optimum process of 10 to 35%.

Lithium Carbonate Filtration

The lithium carbonate can be filtered with a band filter at atemperature of between about 90° C. and 100° C., alternatively betweenabout 92° C. to 95° C., onto a filter with a specially designeddistributor. The filter cake can be washed in a counter current mannerto ensure that the purest lithium carbonate is contacted with freshdeionized water. The wash water is recovered and can be used to washlower purity lithium carbonate. This water can be used to wash thelithium carbonate multiple times to minimize dissolution of lithiumcarbonate in the water. The water recycle step can be particularlyimportant if pure water is scarce. The final wash of the solid lithiumcarbonate is with hot deionized water, which can be supplied through oneor more spray nozzles, at a temperature of between about 80° C. and 95°C., alternatively at a temperature of about 90° C. In certainembodiments it has been determined that washing the lithium carbonateproduct with water at temperatures of greater than about 95° C. resultsin the water turning to steam and washing is ineffective. In certainembodiments, the first wash is completed in a recycle mode, the washwater from the final wash is added to the wash water recycle system,thereby allowing far a much larger volume of water to be used, but notconsumed. As a consequence of the recycling of the wash water, there isa bleed of the wash water, and a part of the wash water can be added toweak liquor recycle to the lithium carbonate dispersion vessel. Incertain embodiments, the first wash water is contacted to the lithiumcarbonate solid at 50 to 90° C.

A Direct Route to Generate High Purity Lithium Carbonate

In one embodiment of the invention, a process for producing high puritylithium chloride from a lithium chloride solution containing up to about1% by weight lithium is provided. In certain embodiments, the lithiumchloride containing solution can be a geothermal brine or other brinesolution, or other chloride containing solution. The first step of theprocess includes treating the lithium chloride solution to adjust the pHto between about 8 and 12, alternatively between about 10 and 12,alternatively between about 10 and 11 with a base, such as for example,lime, sodium hydroxide, ammonia, or the like,) to precipitate salts ofcalcium, manganese, or zinc. The solution is then optionally treatedwith a sodium carbonate solution or with a weak liquor obtained from thebleed of the weak liquor solution. The lithium chloride solution is thensupplied to ion exchange media that is operable to remove traces amounts(typically on the order of parts per billion, or ppb) of divalent ions,and then to a secondary column that is operable to remove boratecompounds that may be present. The lithium chloride is then concentratedby either evaporation or by a combination or reverse osmosis and thermalevaporation (including by natural evaporation from an evaporation pond),to produce a highly concentrated lithium chloride solution, having alithium chloride solution of up to about 42% by weight lithium chloride(the exact concentration is temperature dependent). During the process,the sodium chloride concentration in the solution can be reduced fromgreater than 10,000 ppm to less than 1000 ppm.

The resulting lithium chloride solution, preferably having a lithiumchloride concentration of less than 1000 ppm, can then be reacted at lowtemperatures with a gaseous mixture of ammonia and carbon dioxide toproduce high purity lithium carbonate. The temperature of the solutioncan then be increased to degas the solution, thereby generating ammoniaand hydrochloric acid gases. These gases are separated by known methodsor by membranes.

In another embodiment, the present invention is directed to a method ofproducing high purity lithium compounds, wherein the method includes thefollowing steps:

-   -   (1) feeding a purified lithium chloride stream having an        approximate lithium chloride concentration of 40% by weight to        an electrolyzer equipped with either a membrane or a separator        to prevent migration of cations, such as sodium, lithium, and        potassium, and anions, such as chloride, from migrating in the        direction of the negative electrode;    -   (2) applying a current density of up to about 8,000 A/m² to the        electrolyzer wherein chlorine is generated at the anode, and        hydrogen is generated at the cathode, and a solution that        includes lithium hydroxide is produced in the cathode        compartment (wherein the lithium hydroxide solution has a        concentration of about 4% by weight);    -   (3) cooling the lithium hydroxide solution and feeding the        solution, along with carbon dioxide, to a carbonation reactor        wherein the lithium hydroxide is converted directly to lithium        bicarbonate;    -   (4) separating the lithium bicarbonate containing solution from        the gas and/or any lithium carbonate solids formed;    -   (5) filtering the lithium bicarbonate solution to remove trace        impurities, such as for example, iron, silica, magnesium,        manganese, calcium and strontium;    -   (6) optionally, passing the solution through an ion exchange        column to remove divalent ions that may be present; and    -   (7) feeding the solution to a precipitation reactor where the        solution is heated to a temperature of up to about 95° C. to        precipitate highly pure lithium carbonate.

In certain embodiments, at least a portion of the filtrate solution canbe recycled back to the cathode compartment of the electrolyzer.

Method of Preparing High Purity Chemicals for Batteries

With the high purity lithium carbonate obtained by any of the methodsdescribed above, high purity chemicals can be made by reacting this highpurity lithium carbonate with specific chemicals. As stated previously,“high purity lithium carbonate” refers to any lithium carbonate having apurity of at least about 99.9%. Exemplary reactions include thefollowing:

-   -   (1) reacting high purity lithium carbonate with HF to produce        lithium fluoride solution, following by reaction with PF₅ to        produce LiPF₆;    -   (2) reacting high purity lithium carbonate with HF gas in a        fluidized bed reactor to produce highly pure and dry LiF;    -   (3) reacting high purity lithium carbonate with electrolytic        MnO₂ to produce high purity LiMnO₂;    -   (4) reacting high purity lithium carbonate with cobalt oxide        (CoO₂) to produce high purity lithium cobalt oxide;    -   (5) reacting high purity lithium carbonate with ferric phosphate        to produce lithium iron phosphate;    -   (6) reacting high purity lithium carbonate with phosphoric acid        to produce battery precursors, such as LiH₂PO₄, which can in        turn be reacted with iron oxides to give lithium iron phosphate        cathode powders;    -   (7) reacting high purity lithium carbonate dispersed in        deionized water with gaseous hydrochloric acid to ultra high        purity lithium chloride;    -   (8) a process to produce highly pure electrolyte salts: (a)        triflate, (b) perchlorate, (c) LiASF₅, (d) LiBF₃, and any        others, and (e) lithium bis(oxalate)borate;    -   (9) production of highly pure lithium hydroxide: (a)        electrolysis of lithium bicarbonate solution, by dispersing high        purity lithium carbonate in water and reacting it with carbon        dioxide (b) the electrolysis of high purity lithium chloride        solution produced by reacting high purity lithium carbonate and        hydrochloric acid, and (c) the electrolysis of lithium sulfate        produced from high purity lithium carbonate and sulfuric acid to        produce highly pure lithium hydroxide solution.

In certain embodiments, the preparation of high purity lithium hydroxideinclude supplying a lithium halide to an electrochemical cell whereinthe high purity lithium hydroxide is produced by electrolysis, whilealso producing chlorine and hydrogen gas.

In other embodiments, a lithium salt, for example lithium bicarbonate orlithium nitrate, is supplied to an electrochemical cell wherein it canbe electrolyzed in water to produce high purity lithium hydroxide,hydrogen gas and either H₂CO₃ or HNO₃, respectively.

Alternatively, lithium sulfate can be supplied to an electrochemicalcell and electrolyzed in water to produce high purity lithium hydroxide,H₂SO₄, and hydrogen gas.

In one embodiment, high purity lithium carbonate is reacted with HF toproduce two moles of high purity lithium fluoride and carbon dioxide.The highly pure lithium fluoride is then reacted with PF₅ to produce ahigh purity LiPF₆ product.

In another embodiment, high purity lithium carbonate is reacted with 2molar equivalents HBF₄ to produce 2 moles of high purity LiBF₄, as wellas carbon dioxide and water.

In an alternate embodiment, high purity lithium carbonate is reactedwith 2 molar equivalents of CF₃SO₃H to produce two moles of high purityLi(CF₃SO₃), as well as carbon dioxide and water.

In an alternate embodiment, high purity lithium carbonate is reactedwith 2 molar equivalents of HClO₄ to produce two moles of LiClO₄, aswell as carbon dioxide and water.

Regenerating the Ion Exchange Resin

In another aspect of the present invention, methods for the regenerationof the ion exchange resin are provided.

As used herein, the term “resin” refers to a polystyrene matrix crosslinked with divinylbenzene (DVB) substituted with weakly acidicaminophosphonic or immido acetic acid active groups known by varioustrade names, such as, Amberlite® IRC-746/747/748, Purolite® S 930,Purolite® S 940, Purolite® S 950, LEWATIT® TP-260, IONAC® SR-5, and thelike.

One embodiment 400 of the ion exchange regeneration method, as shown inFIG. 4, is as follows:

-   -   (1) displacing the strong solution from the resin in step 400 by        contacting with deionized water at a low flow rate to prevent        mixing;    -   (2) optionally removing solids and any broken resin (these are        recovered by filtration at the exit of the column) by running a        resin fluidizing backwash of water (i.e., approximately 1.5        bed-volumes in a reverse flow);    -   (3) removing divalent ions from the resin by treating with acid        in step 420, for example, by adding dilute hydrochloric acid        (i.e., a concentration of less than 10%);    -   (4) soaking the column with acid in step 430 for a period of        about 30 minutes;    -   (5) rinsing the resin in step 440 with deionized until a pH of 5        is reached to displace and dilute the acid from the column;    -   (6) optionally, treating the column with base to reactivate the        resin in step 450 by adding dilute NaOH to the column;    -   (7) rinsing the resin with weak liquor to displace and dilute        NaOH from the column;    -   (8) the feed can be returned to loading with the strong liquor        solution in a downflow manner;    -   (9) combining the rinse solutions and recycling the solutions        through reverse osmosis for reuse; and    -   (10) optionally, the wash solutions from steps (3) and (5) can        be recycled.

In an alternate embodiment of the invention, a method is provided asfollows:

-   -   (1) displacing the strong solution from the resin by adding        deionized water at a low flow rate;    -   (2) optionally, removing displaced solids and any broken resin        from the resin by running a backwash;    -   (3) treating the column with acid to remove divalent ions by        adding dilute hydrochloric acid (e.g., HCl having a        concentration of less than about 10%);    -   (4) washing the resin until a pH of about 5 is reached to        displace and dilute the acid on the column;    -   (5) regenerating the ion exchange media by contacting with the        bleed of weak liquor (having a concentration of up to about 14        g/L of lithium carbonate and lithium bicarbonate);    -   (6) rinsing the resin with deionized water to displace and        dilute the column;    -   (7) optionally, the rinse solutions can be combined and recycled        through reverse osmosis for reuse; and    -   (8) optionally, the solutions from steps (3) and (5) can be        recycled.

Microfilter Recycling

Microfilters are expensive and frequently become blocked withimpurities. It is therefore necessary to recycle them. Several methodsof filter recycling have been developed: the preferred methods ofrecycling are to use citric acid to dissolve iron which allows the ironselective filter to be recycled. Other compounds may also be used toachieve this same result, such as sodium EDTA. It is, however, moreeffective to use a strong acid solution, such as nitric acid (having aconcentration of about 1 to 10% solutions) to recycle the filter. Toprevent contamination, the filters are then thoroughly rinsed beforebeing placed back into service.

EXAMPLES Example No. 1 Production of Lithium Carbonate

Referring now to FIG. 1 and FIG. 2, 40 is the dispersion; 45 is thefirst reactor, 50 is the second reactor, 55 is the CO₂ tank, 60 is thegas/solid/liquid separation tank(degasser), 65 is the filter bags, 70 isthe filter cartridges, 75 is the resin columns, 80 is the precipitator,85 is the felt filter, 90 is the dryer, 1 is the impure carbonatestream, 2 is the first reactor feed stream, 3 is the first carbonationreactor, 4 is the second carbonation reactor, 5 is the second reactorfeed stream, 6 is the transfer stream to decanter, 7 is the carbonatereturn stream to first reactor, 8 is the first carbon dioxide recycle, 9is the bicarbonate stream which is supplied to coarse filtration filterbags (such as the liquid filtration bags provided by Eaton-GAF), 10 isthe bicarbonate stream which is supplied to fine filtration cartridgefilters (such as the sterilizing-grade Aervent cartridge filtersavailable from Millipore), 11 is the bicarbonate stream which issupplied to the resin, 14 is the bicarbonate to precipitator, 15 is theexchanger recirculation stream, 16 is a mixed stream that includes therecirculation stream plus bicarbonate stream which is supplied to theprecipitator, 17 is the CO₂ evaporation stream, 18 is the CO₂ returnline to tank 55, 19 is the carbonate stream (which can includecarbonate, bicarbonate or a combination thereof) supplied to filter, 20is the carbonate stream that is supplied to dryer, 21 is the weak liquorwhich is recycled to the dispersion, 22 is the recycle wash water tothat is recycled to the dispersion, and 23 is the wash water bleed.

Referring now to FIG. 2, 95 is a mix tank where recycle stream 126 ismixed with feed stream 124, 100 is an electrolyzer that includes adivision 105 between cathode and anode compartments, which can beachieved with a membrane or diaphragm, 125 is the lithium chloridesolution, 126 is the lithium chloride solution which is the effluent ofthe electrolyzer, 127 is the chlorine gas feed, 128 is the water feed,129 is the hydrogen gas feed, 130 is the lithium hydroxide recyclestream, and 131 is the electrolysis lithium hydroxide product stream.

The processes shown in FIG. 1 and in FIG. 2 are as follows:

The process starts in dispersion tank 40, which can include 3 inputs.Approximately 85% of the feed enters via line 21 as a weak liquor, whichcan be cooled via known means, such as a heat exchanger, to the desiredtemperature. Feed line 21 can have a lithium carbonate/bicarbonateconcentration of about 15 g/L. The mass flow rate of line 21 into tank40 is about 1428 kg/hr. Approximately 15% of the feed is supplied totank 40 via line 22 as recycled wash water, which can be cooled to thedesired temperature by known means. This solution in line 22 can have alithium carbonate/bicarbonate concentration of about 7 g/L and can besupplied at a mass flow rate of about 252 kg/hr. Raw lithium carbonatecan be supplied via screw feeder 1 at a rate of about 30 g/L, and a massflow rate of about 1680 kg/hr, under normal operating conditions. Thethree inputs to tank 40 are mixed with sufficient agitation to maintainthe insoluble lithium carbonate as a uniformly dispersed solidthroughout the tank. An exemplary residence time is 11 minutes. Thesolution is then pumped from tank 40 via line 2 into the first reactor45, where CO₂ gas is supplied via line 3 and is transformed to lithiumbicarbonate and therefore render the lithium soluble.

Referring to FIG. 3, an exemplary reactor 200, which can be similar toor the same as first and second reactors 45 and 50, where such atransformation to lithium bicarbonate may be generated is provided. Incertain embodiments, the lithium carbonate solution is supplied toreactor 200 via line 202 and the carbon dioxide gas is supplied thereactor via line 204. Reactor 200 can be separated into varioussections, for example a first section 206, a second section 208, a thirdsection 210, a fourth section 212, and a fifth section 214. Reactor 200can include various plates separating the various sections, such asplate 222, separating the first and second sections, plate 224,separating the second and third sections, plate 226, separating thethird and fourth sections, and plate 228, separating the fourth andfifth sections. Reactor 200 can also include an agitator 228, positionedwithin the reaction vessel, such that the agitator is capable ofproviding sufficient mixing of the lithium carbonate and carbon dioxide.Agitator 228 can include various blades or protrusions 229 designed toprovide thorough mixing. Reactor 200 can also include baffles 220.Excess carbon dioxide exits reactor 200 via line 230 and the solutioncan be removed via 232.

The flow rate of the carbon dioxide to the reactor can be at least about200 L/min, alternatively at least about 250 L/min. Generally, at least amolar equivalent of carbon dioxide is provided, more preferably slightlygreater than a molar equivalent (i.e., at least about 1.05 molar) isprovided, alternatively greater than about 1.1 molar equivalent isprovided. Solid lithium carbonate can be recycled from the bottom of thedegasser 60 via pump 7 to the bottom of reactor 45. During this stage ofthe reaction, the temperature can increase by about 5° C., due in partto the exothermic chemical reaction that takes place. The solution fromthe first reactor 45 can then be fed via line 5, optionally through aheater exchanger, to the second reactor 50 at a flow rate of betweenabout 1600 kg/hr and about 1700 kg/hr. In certain embodiments, the flowrate is at least about 1500 kg/hr. A heat exchanger can be used to cooldown the fluid to a temperature of about room temperature. Line 4supplies a CO₂ to second reactor 45 at a flow rate of at least about 100L/min, alternatively at least about 120 L/min, alternatively about 135L/min. In certain embodiments, this occurs at a pressure that isslightly above atmospheric pressure, but it can also be run with greaterthrough put at increased pressure. The operating volumes of the firstand second reactors can be about 500 liters each, although reactorshaving different operating volumes may also be used. The solution can becooled to a temperature of about 20° C. and supplied to second reactor50 via pump 5. The heat of the reaction occurring in second reactor 50increases the temperature by about 1 to 2° C. Line 4 supplies CO₂ gas toreactor 50 at a flow rate of about 135 L/min flow. Second reactor 50 canbe a stage reactor similar to the first reactor 45. The temperature inreactor 50 may increase by about 1° C. as a result of the chemicalreaction. Operating second reactor 50 at a temperature below about 20°C. enables the addition of a higher solubility of lithium carbonate intothe solution, which in turn can lead to greater productivity (i.e.,greater through put and higher yield). The bicarbonate containingsolution is transferred via 6 from second reactor 45 to degasser tank60. In degasser tank 60, the gases, solids and liquid are separated.Solids can be pumped as a slurry via line 7 to first reactor 45. Gases,which can include CO₂, can be separated and supplied via line 8, whichcan recycle the gas to CO₂ tank 55, and resupplied to either first orsecond reactor 45 or 50. The liquid bicarbonate is pumped via line 9through at least one, and preferably two, mechanical filter 65. Themechanical filter can include multiple individual filters of varyingsizes, including a first filter comprising a 10 μm filter bag, a secondfilter comprising a 1 μm filter bag. The filtered lithium bicarbonatesolution can be supplied to second mechanical filter 70, which caninclude one or more filter cartridge, for example a first cartridgecomprising a 0.2 μm filter and a second cartridge comprising a 0.3 μmcartridge. The second cartridge can be configured to prevent iron beingfed to ion exchange system 70. The cartridge regeneration process isdiscussed below. The lithium bicarbonate containing liquid solution canbe pumped via line 11 to ion exchange resin column 70. The ion exchangeresin can remove soluble metal divalent ions that pass through thefilter bags 65 and the filter cartridges 70. In certain embodiments, theion exchange 75 can include two columns, one column that is in operationand a second column that is being regenerated. The ion exchange columnscan be switched between operation and regeneration when the operatingmedia becomes saturated. The filtered solution from the ion exchangesystem is fed via line 14 to precipitator 80. Precipitator 80 canoptionally be heated by a recirculation system, which can include a heatexchanger. The solution from precipitator 80 can be fed from bottom ofthe tank and is pumped via line 15 to return line 16. The solution fromthe ion exchange column 75 can be combined in line 16 with the heatedsolution from line 15 and supplied to the precipitator 80. Precipitator80 can be agitated by the flow of line 16. Optionally, precipitator 80can include an agitator. The solution in precipitator 80 can bemaintained at a temperature of about 95° C., which facilitates theseparation of CO₂ from the bicarbonate. The solid carbonate exitsprecipitator 80 by overflow and CO₂ can be cooled and recovered via line17. Carbon dioxide gas can be recycled via line 18 to the two reactors,45 or 50. A product stream that includes about 90% lithium carbonate byweight can be pumped via line 19 to filter band 85. The weak liquor canbe recovered in a vacuum pan system, and can be cooled and pumped vialine 21 to dispersion tank 40. A part of this liquor can be stored forregeneration of the resin. The first wash can be done with the same washrecycle water. The second wash can be done with deionized water at atemperature of about 92° C. Water from each wash can be combined in thesame tank for reuse. This water can be cooled and pumped to dispersiontank 40. There is a bleed line 23 of this water.

Referring to FIG. 2, lithium chloride feed stream 124, having aconcentration of between about 10 and 40%, can be supplied to tank 95,The lithium chloride can be sourced from an extraction process,including geothermal or other brines. Lithium chloride from tank 95 canbe supplied via line 125 to electrolyzer 100. The effluent lithiumchloride solution electrolyzer 100 can be recycled back to tank 95 vialine 126, while chlorine gas and hydrogen gas exits the electrolyzerthrough outlets 127 and 129, respectively. Water is supplied toelectrolyzer 100 via line 128. Lithium hydroxide can be recycled vialine 130 to electrolyzer 100, lithium hydroxide product stream 131 canbe collected. In electrolyzer 100, lithium ions migrate from the anodecompartment to the cathode compartment by way of migration and diffusionforces.

Example No. 2 Loading the Resin to the Column

Resin is loaded into the column, as follows. First, in a 208 L barrel,Purolite® S 940 resin is mixed with deionized water. To a column havinga volume of about 1,060 L was added about a ½ volume of deionized water.Using a funnel, the resin and deionized water are manually added to thecolumn. As needed, the valve at the bottom of the column is opened toempty a little water. The steps are repeated until approximately 440 Lof resin has been introduced to the column.

Example No. 3 Resin Regeneration

In one embodiment of the present invention, a method for theregeneration of the ion exchange resin is provided, as follows:

-   -   (1) strong liquor is removed from the displacement solution and        placed in a holding tank; the strong liquor is replaced with        about 1 bed volume of deionized water that is pumped into the        top of the column at a rate of about 2 to 4 bed-volumes/hour;    -   (2) the resin is unpacked with deionized water and the column is        filled from the bottom of the column with about 1.5 bed volumes        of water at a rate 1.2 bed-volumes/hour;    -   (3) the pH of the solution in the column is lowered to force        resin balls to release retained metal elements and the column        filled with 2 bed volumes of an HCl solution having a        concentration of between about 1-8%, preferably 4%, at a rate of        about 2.4 bed-volumes/hour    -   (4) the acid it is left in place for about 30 minutes;    -   (5) steps (3) and (4) are repeated;    -   (6) the column is rinsed with about 2.1 bed volumes of deionized        water at a rate of about 2.4 bed volumes/hr until the pH of the        column nears neutral pH    -   (7) the column is rinsed with about 2.4 bed volumes of a caustic        soda solution having a concentration of between about 2 and 4%        at a rate of about 2.4 bed volumes/hr to convert the resin back        to the active form to enable the capture multivalent ions    -   (9) about 2.4 bed volumes of weak liquor LiHCO₃ is circulated at        a rate of about 2.4 bed volumes/hr through the column to replace        Na⁺ ions with Li⁺    -   (10) the strong liquor that was temporarily transferred to a        holding tank during the displacement step is returned to the        column at a rate of about 1.2 bed-volumes/hour

Example No. 4

Cartridge filters are very expensive and should be used only once beforereplacement as the plastic around the filter and the cartridges'connections are fragile. In another aspect of the present invention, amethod for the in situ regeneration of cartridges is provided. All thesteps will be done in reverse flow. Referring to FIG. 5, the method 500is shown.

-   -   (1) in first rinsing step 510, about 200 L of deionized water is        circulated through the microfiltration cartridges having        dimensions, for example, of about 2 in. by 40 in., to removing        solid particles;    -   (2) in acid treatment step 520, approximately 5 L of a 20%        solution of HNO₃ is added to about 200 L of deionized water and        is circulated through the cartridges;    -   (3) in second rinsing step 530, about 200 L deionized water is        circulated through the cartridges to remove acid;    -   (4) in a base treatment step 540, about 290 ml of a 50% solution        of a strong base, such as sodium hydroxide or the weak liquor,        is added to about 200 L of deionized water and is pumped through        the cartridges; and    -   (5) in third rinsing step 550, about 200 L of deionized water is        recirculated through the cartridges to removing caustic soda.

In another embodiment of the present invention, a process for makinghigh purity lithium carbonate without first converting the lithiumchloride into solid lithium carbonate is provided as follows:

-   -   (1) a purified lithium chloride stream of approximate lithium        chloride concentration of 40 wt % is supplied to an electrolyzer        equipped with either a membrane or a separator;    -   (2) a current is applied to the electrolyzer and chlorine        generated at the anode, hydrogen generated at the cathode and a        solution of greater than 4% by weight lithium hydroxide produced        in the cathode compartment;    -   (3) the lithium hydroxide solution is cooled and fed, along with        carbon dioxide, to a carbonation reactor where it is converted        directly to lithium bicarbonate;    -   (4) the solution is separated from the gas and any lithium        carbonate solids formed;    -   (5) the lithium bicarbonate solution is filtered to remove trace        impurities including, such as, iron, silica and other        impurities;    -   (6) optionally, the solution is passed through an ion exchange        column to remove divalent ions;    -   (7) the solution is fed to a precipitation reactor and heated to        a temperature of about 95° C. to precipitate highly pure lithium        carbonate; and    -   (8) the solution is recycled back to the cathode compartment for        the electrolyzer.

Example No. 5 Effect of Current

Test #1: The test conditions are shown in Table 1 below.

TABLE 1 Parameters Median Values Current 76.8 A Density of current 6,000A/m² Voltage 5.5 V Flow Rate 210 I/h (0.14 m/s) Test Duration 100minutes Temperature 50-55° C. LiOH (initial) 3.5 M H₂SO₄ (initial) 0.11M Li₂SO₄ (initial) 2.3 M

Nafion 350 membranes were conditioned with a solution of 2% LiOH. Theoutput was calculated by three different manners: LiOH by titration ofthe catholyte, H₂SO₄ by titration of the anolyte, and Li₂SO₄ by eitheranalysis with ion coupled plasma atomic emission spectroscopy or ioncoupled plasma mass spectroscopy of the anolyte. The currentefficiencies were measured by the measurement of three concentrations oflithium hydroxide, sulfuric acid, and lithium sulfate at, respectively,59%; 61%; and 61%. The average current efficiency was 60%.

Test #2: Current density was lowered to 4000 A/m² (51.2 A), the durationwas increased to 135 minutes to allow for a total load of more than400,000 coulombs, as in Test #1 above. The current efficiencies obtainedwere: LiOH=71%, H₂SO₄=59%, and Li_(2SO) ₄=55%, with an average of 62%.

Test #3: The current density was fixed at 3000 A/m² (38.4 A) and theduration at 180 minutes. The current efficiencies were: LiOH=53%,H₂SO₄=62%, and Li₂SO₄=67%, with an average of 62%.

Test #4: The current density was fixed at 3500 A/m² (44.8 A) and theduration at 154 minutes. The current efficiencies were: LiOH=59%,H₂SO₄=62%, and Li₂SO₄=74%, with an average of 62%.

Example No. 6

The objective of the electrolysis process is to convert purified,concentrated LiCl into a concentrated LiOH solution for conversion tolithium bicarbonate, before passing the lithium bicarbonate solutionthrough the process steps described in FIG. 10 at the gas-liquid-solidseparation step, and through the process steps described in FIG. 10 toproduce lithium carbonate. The limiting factor determining theefficiency of the cell is the concentration of lithium hydroxide in thecatholyte, due to back-migration of the hydroxide across the membrane.The experimental program was designed to operate the cell at fourdifferent hydroxide concentrations to map its effect and determine themaximum concentrations that could be prepared.

The experiment measured current efficiency and energy utilization of thedialysis process as a function of hydroxide concentration. As describedin the chemistry section above, Li⁺ ions migrate from the anolyte tocatholyte under the applied electric field, while water is electrolyzedto H₂ and OH⁻ at the cathode. In theory, each electron passed in theexternal circuit corresponds to an increase of one LiOH molecule in thecatholyte, leading to an increase in concentration of LiOH over time.However, the main inefficiency of the process, back migration of Offions from catholyte to anolyte, is dependent on the OH⁻ concentration ofthe catholyte. The experiments reported here were performed with theintention of maintaining the OH⁻ concentration of the catholyte constantby adding water at a known rate. The efficiency of the reaction wasmeasured by comparing the actual rate of addition of water addition withthat expected on the basis of theory.

Experimental Set-Up

The electrolysis system consisted of the electrolysis cell, and theanolyte and catholyte flow systems. Electrolysis of LiCl solutions wascarried out using an FM01 electrolyzer manufactured by ICI (a scalemodel of the FM21 electrolyzer used commercially in the chlor-alkaliindustry). The electrolyzer included lantern blade-style electrodes;ruthenium oxide coated titanium was used as anode and nickel was used ascathode. Nafion® 982 was used as the membrane. The active surface areawas 64 cm² (4×16 cm), and the cell gap was about 12-13 mm. The FM01electrolyzer was operated with the flow direction parallel to the 16 cmdirection, as this improved the management of gasses (chlorine andhydrogen) evolved from the electrodes. In addition, although anolyte andcatholyte flows are normally fed from opposite sides of the cell, theywere fed from the same side in these tests, again to limit the effectsof gas blinding.

The anolyte flow system included a feed tank, pump, degassing tank,chlorine scrubber, and collection tank. A lithium chloride solutionhaving a concentration of about 21% by weight was placed in the anolytefeed tank and heated to about 90° C. The solution was pumped through theanode chamber of the cell in a single pass mode at a flow rate of about20 cm³/min, corresponding to a face velocity of 0.13 cm/s. On exitingthe cell, the LiCl solution and entrained Cl₂ gas (produced at theanode) were passed through into a degassing tank which was equipped witha chlorine scrubber to remove chlorine. The solution was then pumpedinto a collection tank for storage.

The catholyte flow system included a tank, pump and water feed system.Lithium hydroxide was placed in the tank and heated to about 95° C. andwas fed to the cathode chamber of the cell in recirculating mode at aflow rate of about 50 mL/min, corresponding to a face velocity of 0.33cm/s. Water was added continuously to the system using a peristalticpump to try to maintain a constant LiOH concentration. The rate ofaddition was monitored by the weight loss of the water tank. Nitrogenwas bubbled through the catholyte recirculation tank to minimizereaction of LiOH with CO₂ from air.

The experimental conditions used in the four experiments are summarizedin Table 2 below. These conditions were the same for all of theexperiments. The concentration of hydroxide in the, catholyte was variedfrom 2.5 M to 0.7 M between the four experiments.

TABLE 2 Summary of main parameters used in the electrolysis experimentsperformed. Parameter Value Current Density 3000 A m⁻² Electrode Area 64cm² Anolyte Volume 60 cm³ Catholyte Volume 60 cm³ LiCl InletConcentration 21 wt % LiCl inlet pH 0.5-0.7 Temperature 90° C. Time ofOperation 2-3 hours Anolyte (LiCl) Flow Velocity 0.13 cm/s Catholyte(LiOH) Flow Velocity 0.33 cm/s

Samples were collected at the catholyte inlet and outlet and anolyteoutlet ports every 30 minutes during operation of the cell. The cellvoltage was monitored at the cell terminals using a handheld multimeter.The difference between the inlet and outlet catholyte hydroxideconcentrations and the cell voltage were used to calculate theefficiency and energy consumption of the cell.

Results

Referring now to FIG. 6 to FIG. 9 and Table 3, the results of the fourexperiments are summarized. FIG. 6 shows the difficulty in maintaining aconstant LiOH concentration based solely by adjusting the rate of wateraddition, in the absence of a real-time measurement of the hydroxideconcentration. This is believed to be because water can be consumed oradded to the catholyte by a variety of mechanisms, includingelectrolysis, evaporation and migration across the membrane with Li⁺cations. In general, the data suggest that the higher the initialconcentration of LiOH, the more difficult the task of maintaining theconcentration constant through water addition.

The cell voltage was approximately 4.3-4.4 V for all of the experimentalruns (shown in FIG. 7), indicating that the voltage is relativelyindependent of hydroxide concentration. It also implies that energyconsumption is largely driven by the electrical efficiency of theelectrode and membrane reactions. The cell gap in the FM01 electrolyzerused in the study (12-13 mm) is large, as compared to commercial cells(2-3 mm), so a commercial cell would be expected to have a lower cellvoltage than those measured here.

The current efficiency decreases with increasing LiOH concentration, asshown in FIG. 8. This is likely due to increased back-migration of OH—anions across the membrane from the catholyte to anolyte as the LiOHconcentration increases. As shown in FIG. 9, this phenomenon alsoresulted in an increased energy consumption because all experiments wereperformed at about the same current density and the cell voltage wasessentially constant. The data suggests that the practical limitingconcentration of LiOH is about 1-2 M, although it may be possible toidentify a range of operating conditions or other membranes which wouldachieve a different result.

Table 3 summarizes the findings of this study and shows that theefficiency of LiOH production increases as the concentration of LiOHdecreases, reaching an efficiency of between about 80-88% forconcentrations of about 1 M (2.4 wt %) LiOH. Cell voltage is relativelyindependent of LiOH concentration, so efficiency also drives the energyrequirement, which decreases to about 5 kWh per kg LiOH produced at aconcentration of about 1 M. The LiOH production rate is also maximum(2.1-2.4 kg/m2/hr) at 2.4 wt % LiOH concentration.

TABLE 3 Summary of the main results of the experimental program. Pro-duction Cell Rate* LiOH LiOH Volt- Water Effi- kg Energy Test (Start)(Final) age Add ciency LiOH/ kWh/kg ID M M V g/min % m²/hr LiOH June 82.57 3.28 4.37 0.5 35 0.94 15 June 1.62 1.88 4.45 5 65 1.74 8 10 June0.94 0.92 4.28 11 80 2.14 5 12 June 0.69 0.89 4.33 10 88 2.36 5.3 15*Calculated from data (Production rate = 2.68 kg LiOH/m²/hr ×efficiency).

Example 7 Purified Lithium Carbonate Starting from Solid LithiumHydroxide

Dispersion

Solid lithium hydroxide monohydrate was fed at approximately 43.3 kg/hrto dispersion tank 40 via line 1, and recycled wash water and weakliquor are recycled via lines 21 and 22 respectively. The total flowrate to the tank being about 22 kg/min., about 80% of the flow was weakliquor and the remaining flow is wash water. The resulting mixture was asolution of lithium carbonate and hydroxide. The solution temperaturewas approximately 20° C.

Reaction

The rate of reaction for the conversion of lithium hydroxide to lithiumcarbonate and bicarbonate was controlled by maintaining a pH on theoutlet side of the first reactor 45 at about 8.5. The CO₂ flow to thefirst reactor 45 was adjusted to maintain this pH. The CO₂ flow rate wasabout 300 L/min and the temperature of the solution exiting the reactorwas increased to approximately 30° C., due to the heat of reaction. Thesolution temperature was cooled to 20° C. by way of the heat exchangerbetween the first and second two reactors, 45 and 50.

The second reactor converted the remaining unconverted lithium carbonateinto lithium bicarbonate as CO₂ was fed to the second reactor at a flowrate of 275 L/min and the temperature on the outlet side of the reactorwas increased to about 23° C. due to the heat of reaction.

The lithium bicarbonate solution was then passed through the sameprocess and under the same conditions as in Example 1. First thesolution passes through to the gas/solid/liquid separator 60, thenthrough filtration 65 and 70, ion exchange 75 and to the precipitator 80and on to filtration 85 and drying 90.

Resin

The lithium hydroxide monohydrate had a significantly lowerconcentration of calcium and magnesium than lithium carbonate. It wastherefore possible to increase the time between regenerations to between60 and 90 bed-volumes of strong liquor.

Filter Band

The flow rate of the second washing was adjusted to 3 L/min of deionizedwater heated to 92° C. The flow rate of the first wash was the same asin Example 1.

Drier

The dryer operated as described in Example 1, producing approximately35.83 kg/hr of purified lithium carbonate. The chemical yield was ataround 93%.

Example No. 8 Production of Lithium Carbonate

In FIG. 1, the system for the production of high purity and ultra highpurity lithium carbonate includes dispersion tank 40 that is configuredto provide a suspension of particles; first carbonation reactor 45,second carbonation reactor 50, CO₂ tank 55, gas/solid/liquid separationtank (degasser) 60, first filtration system 65 that includes filterbags, second filtration system 70 that includes filter cartridges, ionexchange columns 75, precipitator 80, belt filter 85, and dryer 90. Feedline 1 supplies impure carbonate to the reactor, feed to the firstreactor is via line 2, CO₂ is fed to the first reactor via line 3, CO₂is fed to the second reactor via line 4, lithium carbonate is fed to thesecond reactor via line 5, lithium carbonate from the second reactor istransferred to the decanter via line 6, a portion of the carbonate isreturned to the first reactor via line 7, degassed CO₂ is removed vialine 8, bicarbonate is supplied to filter bags via line 9, bicarbonateis supplied to the cartridges via line 10, bicarbonate is supplied tothe ion exchange resin via line 11, bicarbonate is supplied to theprecipitator via line 14, heat exchanger recirculation is via line 15,line 16 supplies a mixture of the recirculation from the precipitatorand bicarbonate from the ion exchange resin to the precipitator, CO₂separated by the precipitator is recycled via line 17, CO₂ from recycleline 17 and degasser line 8 is supplied to holding tank via line 18,carbonate is supplied to the filters via line 19, filtered carbonate issupplied from the filters to the dryer via line 20, weak liquor from thefilters is supplied to the dispersion tank via line 21, recycled washwater is supplied from the filters to the dispersion tank via line 22,and wash water bleed is removed from the filters via line 23.

As is understood in the art, not all equipment or apparatuses are shownin the figures. For example, one of skill in the art would recognizethat various holding tanks and/or pumps may be employed in the presentmethod.

The singular forms “a”, “an” and “the” include plural referents, unlessthe context clearly dictates otherwise.

Optional or optionally means that the subsequently described event orcircumstances may or may not occur. The description includes instanceswhere the event or circumstance occurs and instances where it does notoccur.

Ranges may be expressed herein as from about one particular value,and/or to about another particular value. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value and/or to the other particular value, along withall combinations within said range.

Throughout this application, where patents or publications arereferenced, the disclosures of these references in their entireties areintended to be incorporated by reference into this application, in orderto more fully describe the state of the art to which the inventionpertains, except when these reference contradict the statements madeherein.

As used herein, recitation of the term about and approximately withrespect to a range of values should be interpreted to include both theupper and lower end of the recited range.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereupon without departing from the principle and scope of theinvention. Accordingly, the scope of the present invention should bedetermined by the following claims and their appropriate legalequivalents.

1. A method of producing high purity lithium carbonate, comprising thesteps of: reacting a first aqueous solution comprising a technical gradeLi₂CO₃ with CO₂ to form a second aqueous solution comprising dissolvedLiHCO₃; separating unreacted CO₂ and insoluble compounds from the secondaqueous solution using a gas-liquid-solid separator to produce a thirdaqueous solution, removing dissolved impurities from the third aqueoussolution by contacting the third aqueous solution with an ion selectivemedium to produce a fourth aqueous solution; and precipitating Li₂CO₃from the fourth aqueous solution, wherein the Li₂CO₃ has a purity of atleast about 99.99%.
 2. The method according to claim 1, wherein theinsoluble compounds separated from the second aqueous solution arerecycled to the first aqueous solution.
 3. The method according to claim1, further comprising the step of preheating the third aqueous solutionto a temperature of about 50° C. before precipitating Li₂CO₃.
 4. Themethod according to claim 1, further comprising the step of supplyingthe third aqueous solution to a reverse osmosis apparatus to concentratethe Li₂CO₃, wherein the reverse osmosis apparatus is operable to removeCO₂ from the solution and cause Li₂CO₃ to precipitate.
 5. A method ofproducing high purity lithium carbonate, comprising the steps of:contacting an aqueous brine containing LiHCO₃ having a purity of lessthan about 99% with CO₂ at ambient temperature to form a second aqueoussolution comprising LiHCO₃ and dissolved ions; separating insolublecompounds from the second aqueous solution using a glass-liquid-solidreactor to form a third aqueous solution, the third aqueous solutioncomprising LiHCO₃ and dissolved ions; extracting at least a portion ofthe dissolved ions from said third aqueous solution with an ionselective medium to form a fourth aqueous solution containing thedissolved LiHCO₃ and having a reduced concentration of dissolved ionsrelative to the third aqueous solution; maintaining a constant pressurewhile carrying out the separating and extracting steps; and heating thefourth aqueous solution to form solid LiHCO₃, gaseous CO₂ and dissolvedimpurities.
 6. The method according to claim 5, wherein the insolublecompounds separated from the second aqueous solution are recycled to thefirst aqueous solution.
 7. The method according to claim 5, furthercomprising the step of supplying the second aqueous solution to areverse osmosis apparatus, wherein said reverse osmosis apparatus isconfigured to operate at high pressures, thereby concentrating theLi₂CO₃.
 8. A method of producing highly pure LiPF₆, the methodcomprising the steps of reacting high purity Li₂CO₃ obtained accordingto the method of claim 1 with HF to produce lithium fluoride solution;and reacting the solution with PF₅ to produce LiPF₆.
 9. A method ofproducing highly pure LiF, the method comprising the steps of reactinghigh purity lithium carbonate prepared according to the method of claim1 with HF gas in a fluidized bed reactor, wherein the LiF is highly pureand dry.
 10. A method of producing highly pure LiMnO₂, the methodcomprising the steps of reacting high purity lithium carbonate preparedaccording to the method of claim 1 with electrolytic MnO₂ to producehigh purity LiMnO₂.
 11. A method of producing highly pure lithium cobaltoxide, the method comprising the steps of reacting high purity lithiumcarbonate prepared according to the method of claim 1 with cobalt oxideto produce high purity lithium cobalt oxide.
 12. A method of producinghighly pure lithium iron phosphate, the method comprising the steps ofreacting high purity lithium carbonate prepared according to the methodof claim 1 with high purity ferric phosphate to produce high puritylithium iron phosphate.
 13. A method of producing highly pure LiH₂PO₄,the method comprising the steps of reacting high purity lithiumcarbonate prepared according to the method of claim 1 with phosphoricacid to produce highly pure LiH₂PO₄.
 14. The method of claim 13, furthercomprising reacting the LiH₂PO₄ with iron oxide to produce lithium ironphosphate.
 15. A method of producing highly pure lithium chloride, themethod comprising the steps of reacting a solution comprising deionizedwater and high purity lithium carbonate prepared according to the methodof claim 1 with gaseous hydrochloric acid to produce highly pure lithiumchloride.
 16. A method of producing highly pure electrolyte salts, themethod comprising the steps of reacting high purity lithium carbonateprepared according to the method of claim 1 by either triflation orperchloration and using LiASF₅, LiBF₃, lithium bis(oxalate)borate, orcombinations thereof.
 17. A method of producing highly pure lithiumhydroxide by electrolyzing a solution comprising highly pure lithiumbicarbonate, wherein the highly pure lithium bicarbonate has beenprepared according to the method of claim
 1. 18. A method of producinghighly pure lithium carbonate, the method comprising the steps of:feeding a first aqueous solution comprising a purified lithium chloridestream to an electrolyzer equipped with a membrane or a separator,wherein the first aqueous solution has a lithium chloride concentrationof up to about 40% by weight to form a second aqueous solutioncomprising at least 10% by weight lithium chloride; applying a currentto the electrolyzer to produce a third aqueous solution in the cathodecompartment that comprises greater than 4 wt % lithium hydroxide;optionally cooling the third aqueous solution and supplying the thirdaqueous solution and carbon dioxide to a carbonation reactor to producea fourth aqueous solution comprising lithium bicarbonate; separating thefourth aqueous solution from the carbon dioxide and lithium carbonatesolids formed using a gas-liquid-solid reactor; filtering the fourthaqueous solution to remove trace impurities; and feeding the filteredfourth aqueous solution to a precipitation reactor maintained at atemperature of at least about 95° C. to precipitate highly pure lithiumcarbonate.
 19. The method of claim 18, further comprising supplying thefourth aqueous solution following the filtration step to an ion exchangecolumn to remove divalent ions.